Means and method for producing expanded metal

ABSTRACT

The invention relates to a method of producing an expanded metal product wherein the metal sections are stretched instead of being bent so as to achieve the expanding process. The method is characterised by forming a series of parallel rows of slots each of identical size and each having curved ends, the slots of alternate rows being staggered and overlapping so as to form a series of longitudinally extending stretchable portions, the metal edges being clamped and then moved apart in a transverse direction so as to strain the stretchable portions beyond their yield point and to incline them to the longitudinal direction.

United States Patent 1191 Ju y MEANS AND METHOD FOR PRODUCING EXPANDED METAL [75] Inventor: Harold RexJury,Norw odd:

Australia [73] Assignee: Jury & Spiers Proprietary Limited,

Norwood, South Australia, Australia 22 Filed: July 13,1951" [21] Appl.No.: 162,135

[30] Foreign Application Priority Data July 16, 1970 Australia 1859 52 us. at. 29 61 51] 1nt.Cl B2ld 31 04 [58] Field of Search 29/6.1

[56] References Cited UNITED STATES PATENTS 1,103,033 7/1914 Clark 29/6.1 3,618,185 11/1971 Coeri 29/6.l 1,802,011 4/1931 Frease 29/6.1

1111 3,774,274 1 Nov. 27, 1973 2,290,486 7 1942 Ballard et al. 29 e.1 885,548 4/1908 Turnbull 29/6.I 845,764 571907" 7 2976.1

1 1/1967 Johnson 29/6.'l

Primary ExaminerAndrevv R. Juhasz Assistant ExaminerLeon Gilden Att0rney-Jay L. Chaskin et al.

57 ABSTRACT The invention relates to a method of producing an expanded metal product wherein the metal sections arestretched instead of being bent so as to achieve the ex-- panding process.-

transverse direction so as to strain the stretchable portions beyond their yield point and to incline them to the longitudinal direction.

6 Claims, 7 Drawing Figures Patented Nov. 27, 1973 3,774,274

3 Sheets-Sheet 2 Patented Nov. 27, 1973 3 Sheets-Sheet 5 This invention relates to a means for and a method of producing expanded metal shapes in the form of a mesh which can be used either for structural or decorative purposes.

So called expanded metal is currently produced by a process wherein a sheet of metal is sheared to produce staggered rows of slits, and the material is'pulled in a direction which is transverse of the rows to produce a steel mesh having a series of diamond pattern openings. The ends of the slits constitute zones of extreme stress, having been stressed almost to the point of shearing during the shearing process of the slits, but even if this were not so, the stress concentration would become very large as the metal is expanded, due to shape of the metal edges defining the slit end. The combined effects of semi-shearing and shape result in tearing of the metal during expansion. To overcome this difficulty the metal is sometimes bent out of the plane of the original metal between the strips, and the bent metal flexes as the sheet is expanded, reducing stresses at the slit ends. Another alternative procedure which is frequently used to reduce tearing or for formation of cracks at the ends of the slits is for the metal to be allowed to reduce in length as it is increased in width. This becomes possible since the slits are usually carried outwardly to adjacent the edges of the sheet of metal which is to be expanded, the outer chords being bent during the expansion. However, in both of the above configurations the expanded metal has very little structural strength. Since either the strips of metal between the slits are of bent formation, or alternatively the outer edges are free to change their dimensional length as the openings are expanded, or both, the panel must be essentially regarded as a flexible panel and is not suitable, for example, for use as a structural member arranged to support loads of the same magnitude as would normally be supported by a member having the configuration of a truss and having the struts thereof with the same cross-sectional area as the strips of the formed metal which define the diamond openings.

One of the objects of this invention therefore is to provide improvements whereby expanded metal has sufficient inherent rigidity to be load bearing.

Another of the difficulties which is encountered with expanded metal of the configuration described above is that the diamond shape pattern, although regular, contains the abovementioned sharp corners which are formed by those portions of the metal which were originally the portions forming the ends of theslits. For many purposes such metal is aesthetically acceptable, but for some purposes it is not, and a further object of this invention is to provide a configuration which will be aesthetically more acceptable than thev above defined configuration.

In one of the forms of this invention, the method of producing an expanded metal product comprises at least partly perforating a ductile metal member so as to at least partly form a plurality of slots, the slots being of identical shape and size and having curved ends, and being equally spaced in each of the series of parallel rows the longitudinal axes of which are co-incident with the longitudinal axes of the slots contained therein, the pitch centre distance of the slots in any one row being only slightly greater than the slot length and '2 the slots of any one row being staggered with respect to the slots of the nextadjacent row so as to, form from the metal member a series of longitudinally extending stretchable portions between the rows, clamping the metal member between two pairs of transversely spaced longitudinally extending clamp jaws, forcing said pairs away from each other in a transversedirection thereby both straining saidstretchable portions beyond their yield point and inclining therntojsaid, relative longitudinal axes, and releasing the clamps'from the expanded metal products. so formed,

By clamping the metal'member between the two pairs of clamp jaws, reduction in overall length of the member is substantially avoided andthe stretchable portions of the member are therefore strained to provide the requiredinclination relative to their original longitudinal axes, instead of .theinclination being achieved solely, or mainly, by bending of themetal. This straining has the'effect of increasing the ultimate tensile strength and also the ultimate compression strength of the struts of the member for practically all known ductilemetals whichare suitable foruse as expanded metal, and the final product is very much stiffer than a similar product made by previously usedmethods. The employment of slots having rounded ends avoids the very high stress concentrationswhich exist at the ends of slits, since the slots maybe fully sheared at their ends, and when the straining of a metal takes place as the clamps are moved apart, thestress at the ends of the struts so formed is spreadover a considerable area of metalat the ends of the slots thus reducing stress concentration and allowing the straining of he struts to take place without cracking ofthe parent metal.

The curved ends of the slots may be formed by. pressing or punching, either completely shearing orpartly shearing'the slugs from the parent metal, but this, operation is necessarily a somewhat slow operation. A: further object of' the invention therefore ism-provide means for producing an expanded metal, product produced by the method defined above, and in one of its forms this includes a main frame having twopairs of bearings defining a pair of spaced parallel axis, a pair of rolls rotatable in respective said pairs of bearings, the first of said rolls having a plurality of axially spaced, radially outstanding and circumferentially extending projections having curved ends, and the second of said rolls having a surface spaced radially away from said projections to define therebetween a slug accommodating space, the means being so constructed and arranged that when a ductile metal member to .be expanded is driven between the rolls, the projections atleastpartly perforate the member to thereby form the plurality. of slots in accordance with the method defined, that is, slots having identical shape and size and curved ends, and being equally spaced in each of a series of parallel rows, the longitudinal axes of which are,coinci dent with the longitudinal axes of the slots contained therein, the pitch centre distance of the slots in anyone row being only slightly greater than the slot lengthand the slots of any row being staggered with respect to. the slots of the next adjacent row so as to form from the metal member a series of longitudinally extending stretchable portions between the rows. It is foundin practice desirable to have the projections arranged "with respective circular surfaces forthe shearing of the metal, and the surface of the second roll. which is spaced radially away from a respective projection may be the base of a female die, or alternatively the second roll may have I a cylindrical surface if the expanded metal product has a plurality of ribs of sufficient strength to support the member against collapse as the projections shear the slots. In each case the slug is accommodated in the radial space existing between the radial projections and the surface of the second roll.

Two embodiments of the invention are described hereunder in some detail with reference to and are illustrated in the accompanying drawings in which:

FIG. 1 is an enlarged fragmentary section showing the partial shearing of a slug of metal from a ductile metal member which is subsequently to be expanded,

FIG. 2 is a plan view of a metal member (of indefinite length), drawn to a smaller scale than in FIG. 1, and showing a plurality of slots partly sheared from a duetile metal member,

FIG. 3 is a somewhat diagrammatic representation of a stretching frame with two pairs of clamp jaws thereon for stretching of the metal member of FIG. 2,

FIG. 4 shows the metal member of FIG. 2 after the clamps have been forced away from each other in a transverse direction, and the stretchable portions of the member of FIG. 2 strained beyond their yield point and inclined relative to the longitudinal axes of the rows of slots,

FIG. 5 is a fragmentary enlarged view illustrating the way in which the curved ends of the slots open up without subjecting the metal to such severe stress concentration as to form cracks therein,

FIG. 6 is a transverse section of a member according to a second embodiment, the member being formed with ribs of sufficient strength to prevent collapse during the shearing of the slots, and

FIG. 7 is a section taken on line 77 of FIG. 6.

Referring to the first embodiment of FIGS. 1 to 5, a main frame which is not ilustrated therein is provided with two pairs of bearings which define two spaced parallel axes, and a pair of rolls, respectively designated 1 l and 12, are rotatable in the pairs of bearings.

The upper roll 11 is provided with a series of projections designated 13, the projections standing outwardly from a cylindrical surface 14 on the roll 11, the projections being spaced from each other axially across the roll in the direction of the axis of the roll, being outstanding from the surface 14 in a radial direction, and extending circumferentially around the surface 14 for most but not all of the circumference. The projections 13 are provided with curved ends 16. The second or lower roll 12 is provided with a corresponding series of axially spaced radially extending grooves 17 which constitute the female die portion of the rolls, each groove 17 having its inner surface 18 spaced radially away from the respective projection 13 as shown in FIG. 1, thereby providing a slug accommodating space for the accommodation of a slug 20 which is partially or fully sheared by a roll shearing action of the projection 13 from a ductile metal member 21 which is subsequently to be expanded. The radially extending side walls of the grooves 17 co-operate with the projections 13 to constitute a shear die set.

In this embodiment the ductile metal member 21 is an aluminum sheet which conforms to S.A.E. Standard 6063, although other ductile metal is known to be satisfactory for the invention. The slugs 20 are only partly sheared from the member 21, being retained by a small area of unsheared metal, this obviating a scrap problem which is encountered with rolls if the slugs can inadvertently be carried around by the walls of the groove 17. Because the projections 13 have curved ends 16, the slugs 20 and the corresponding slots formed by their partial removal from the metal member 21 also have curved ends as shown in FIG. 2. The slots are all of identical shape and size, and are equally spaced in each of the series of rows designated 23, the longitudinal axes of the rows 23 being co-incident with the longitudinal axes of the slots contained therein, and the pitch center distance marked P.C.D. of the slots of any one row being only slightly greater than the slot length so that the interconnecting portions 24 are relatively short. As shown in FIG. 2, the slots of any one row are staggered with respect to the slots of the next adjacent row or rows, and thereby form between the rows a series of longitudinally extending stretchable portions which are designated 25.

FIG. 3 shows a further stage in the method of producing an expanded metal product, wherein the ductile metal member 21 of FIG. 2 is clamped between two pairs of transversely spaced longitudinally extending clamp jaws. In FIG. 3, a stretching frame 27 has one of the pairs of clamp jaws designated 28 secured thereto by securing means which are not illustrated, and the stretching frame 27 also has guides 29 for the guiding of the second set of clamp jaws 30 which are movable, while a hydraulic cylinder 31 operatively interconnects the movable clamp jaws 30 and the stretching frame 27. Each of the pair of clam jaws 28 and 30 is provided with a fixed jaw member 33 and a movable jaw member 34 driven by a clamping cylinder 35. When the ductile metal member has been clamped as shown in FIG. 3, the hydraulic cylinder 31 is operated to thereby force the pairs of clamps 28 and 30 away from each other, in a direction which is transverse of the slots, and this movement has the effects of tearing the unsheared metal of the slots thus ejecting the partially sheared slugs 20, stretching the longitudinally extending stretchable portions 25, and forming the expanded metal product 38 which is illustrated in FIG. 4. FIG. 5

shows the manner in which the stress concentration is spread over an area of metal designated A, and this is found to substantially avoid fracture with most ductile metals if the radius of each of the curved ends 16 is not less than half the thickness of metal.

In the second embodiment which is illustrated in FIGS. 6 and 7, the upper roll 41 co-operates with the lower roll 42. In this embodiment a main frame 43 carries on it two pairs of bearings respectively designated 44 and 45 which define two spaced parallel axes, and the rolls 41 and 42 are respectively joumalled in the bearings 44 and 45. As in the first embodiment, the upper roll 41 carries on it the axially spaced radially projecting and circumferentially extending projections 13, but the projections 13 of the upper roll 41 project radially outwardly further than those of the roll 11 of the first embodiment so as to completely shear slugs 20 as shown in FIG. 6. The ductile metal member designated 47 is not in the form of a flat sheet as in the first embodiment, but is formed from extruded aluminium and has a plurality of spaced flanges 48 joined by narrow webs 49, the width of each of the webs 49 being substantially the same as the thickness of the projections 13 thereby avoiding the need for a female die arrangement. The lower roll 42 merely has a single cylindrical surface which functions to back-up the flanges 48 by simply bearing against them during shearing of the slugs 20 from the webs 49, and the space between the webs 49 and the surface of the roller 42 is sufficient to accommodate the slugs 20.

This is further illustrated in FIG. 7, which is a section taken on line 7-7 of FIG. 6. FIG. 7 illustrates the manner in which the webs 49 have the slugs 20 removed therefrom.

When the product to be expanded is a considerable width in a transverse direction (for example exceeding say six rows of slots) there is a tendency for the ends to draw inwardly during the stretching operation. In all instances this is avoided by the simple expedient of inserting pins through the or some of the end slots, the pins engaging against restraining members in the stretching machine.

What I claim is:

1. The method of producing an expanded metal product which comprises the steps of advancing a ductile metal member between a set of rotatable roll shears to at least partly perforate the member so as to at least partly form a plurality of slots extending substantially longitudinally in the direction of the advance, the slots being of identical shape and size and having curved ends, and being equally spaced in each of a series of parallel rows the longitudinal axes of which are coincident with the longitudinal axes of the slots, the pitch centre distance of the slots in any one row being only slightly greater than the slot length and the slots of any row being staggered with respect to the slots of the next adjacent row,

from the transversely uct according to claim 1 wherein each of said slots is partly formed by partly shearing said ductile metal member to form a slug, partly sheared metal retaining the slug to the ductile metal member until said jaws are displaced away from each other said displacing tearing said partly sheared metal and removing said slugs from the member.

3. A method of producing an expanded metal product according to claim 1 wherein each of said slots is formed by fully shearing a slug from said ductile metal member before said clamping of the member.

4. A method of producing an expanded metal product according to claim 1 wherein said ductile metal member is a sheet of a metal having constant thickness.

5. A method of producing an expanded metal product according to claim 1 wherein said ductile metal member has a constant cross-section sectional shape which includes a plurality of spaced flanges joined by narrow webs.

6. A method of producing an expanded metal product according to claim 5 wherein one of said rolls bear against said flanges while projections on the other roll shear portions of said web between the flanges. 

1. The method of producing an expanded metal product which comprises the steps of advancing a ductile metal member between a set of rotatable roll shears to at least partly perforate the member so as to at least partly form a plurality of slots extending substantially longitudinally in the direction of the advance, the slots being of identical shape and size and having curved ends, and being equally spaced in each of a series of parallel rows the longitudinal axes of which are coincident with the longitudinal axes of the slots, the pitch centre distance of the slots in any one row being only slightly greater than the slot length and the slots of any row being staggered with respect to the slots of the next adjacent row, clamping the partly perforated metal member between a pair of jaws, displacing said jaws away from each other in a direction transverse to the longitudinal axes of the slots until the ductile member is strained beyond the yield point to complete the shearing of the slots and releasing the clamp jaws from the transversely expanded metal member.
 2. A method of producing an expanded metal product according to claim 1 wherein each of said slots is partly formed by partly shearing said ductile metal member to form a slug, partly sheared metal retaining the slug to the ductile metal member until said jaws are displaced away from each other said displacing tearing said partly sheared metal and removing said slugs from the member.
 3. A method of producing an expanded metal product according to claim 1 wherein each of said slots is formed by fully shearing a slug from said ductile metal member before said clamping of the member.
 4. A method of producing an expanded metal product according to claim 1 wherein said ductile metal member is a sheet of a metal having constant thickness.
 5. A method of producing an expanded metal product according to claim 1 wherein said ductile metal member has a constant cross-section sectional shape which includes a plurality of spaced flanges joined by narrow webs.
 6. A method of producing an expanded metal product according to claim 5 wherein one of said rolls bear against said flanges while projections on the other roll shear portions of said web between the flanges. 